The present invention relates to an ink supply system for printers. More particularly, the present invention relates to an ink supply with viscosity control for a printing system.
Automated printing systems are in widespread use in a host of industries. And, the number of types of printing systems is almost as great as the number of industries in which these systems are used.
One type of printing system that operates in a fully automatic or near fully automatic mode is a pad printing system. These systems are used to apply high quality print, e.g. indicia, on flat as well as non-flat surfaces. For example, pad printing systems can be used to print logos and the like on cellular telephone covers, game balls such as golf balls and the like. It will be appreciated that such printing must be carried out, not only on a spherical surface, but on a surface that is formed with dimples as well.
Conventional pad printing systems use a deformable pad which receives ink, transferred as an image, from a flat cliché plate. The plate has an engraving or etching of the indicia formed therein. Ink is transferred from an ink supply to the plate, and fills into the etched areas. The deformable pad is then pressed onto the plate and the ink is picked up by the pad. The image is the transferred to the curved surface which is to be printed. To re-ink the pad, in a commonly used arrangement, an inverted cup containing a quantity of printing ink is used to apply the ink to the cliché plate. To apply a new coating of ink to the cliché plate, the ink cup and cliché plate are moved relative to each other following each ink transfer operation. A doctor blade is fitted to the cup to traverse along the cliché´ plate and “wipe” the cliché plate. This assures that ink is left behind in the etching but does not build up on the plate, inside or outside of the etched areas.
The ink supply system is configured to maintain a fresh flow or supply of ink to the ink cup so that the ink transferred to the cliché´ plate is likewise fresh. It is also designed so that the viscosity of the ink is controlled to maintain the flow characteristics within certain desired parameters. The ink flow characteristics are generally maintained to achieve proper ink pick-up (from the plate to the pad) and transfer (from the pad to the object), as well as to achieve good print quality.
In a typical ink supply system, the ink is pumped from a source or supply to the ink cup. As such, the ink entering the cup is under pressure which can adversely effect the seal between the doctor blade and the cliché´ plate. This can also effect the quantity of ink that is deposited in the etching as well as outside of the etching, as well as the flow characteristics of the supplied ink.
Accordingly, there is a need for an ink supply system for a printing system that provides the ability to maintain control of the flow characteristics of the supplied ink. Desirably, such a system operates without pressurizing the ink cup into which the ink is supplied.